Phonograph tone arm supporting and adjusting arrangement



| c. AMMLUNG, JR

Filed Sept. 9, 1948 March 4, 1952 PHONOGRAPH TONE-ARM SUPPORTING ANDADJUSTING ARRANGEMENT Patented Mar. 4, 1952 PHONOGR-APH TONE ARMSUPPORTING AND ADJUSTING ARRANGEMENT Louis C. Ammlung,'Jr.,Philadelphia, Pa., assignor to Philco Corporation, Philadelphia, Pa., acorporation' of Pennsylvania :Application September 9, 1948, Serial No.48,426

5 Claims. (01. 274-23) The present invention relates to phonographtone'arms and, particularly, to an improved arrangement capable ofsupporting the tone-arm in proper position to insure adequate trackingengagement of the pickup needle with the modulated groove of a record.Specifically, the invention has to do with improvements in the bearingsupport structure for the tone-arm shaft whichjprovides forswingingmovement of the tone-arm about an axis perpendicular to the playingsurface of a. record.

It is wellknown in the art that, in order to insure proper tracking andhigh fidelity reproduction, the tone-arm should be supported in adefinite angular relationship with respectto the record-and the tone-armsupporting structure should be capable of damping out andeliminating.undesirable vibrations, so as to prevent the eifects ofresonance occurring in the tone-arm during normal use of the phonograph.In many cases, arrangements used for the. above stated purposes areobjectionable because of the complicated and expensive structure theyrequire.

For example, known arrangements for the mentioned purposes necessitateaccurate machining and skillful assembly techniques, which result inincreasing manufacturing and production costs.

It-is, therefore, the primary object of the present invention to providea tone-arm supporting arrangement which realizes the above-mentioneddash-abilities; and which eliminates the aforesaid objections. To thatend, the supporting arrangementis of such character that the bearingmeans for the pivot-providing shaft of the tone-arm consists of easilymade parts which are capable of beingreadily associated with thephonograph structure to. support and to maintain said shaft in properposition, and which. are further capatale of absorbing undesirablevibrations.

It is also an object of the invention to provide a tone-arm supportingarrangement of the above-mentioned character, in which the parts areassociated in such a manner that the tonearm may be quickly andaccurately adjusted in proper operative position. For that purpose, thesupporting arrangement includes two separate bearings which are adaptedto be mounted in approximate alignment on the phonograph struc v tureand which, when so mounted, are capable of'being: relatively adjusted inthe required relationship to support the tone arm for operative trackingengagement of the pickup needle with the'record' groove.

- Another and more specific object of the invention resides in theprovision of a tone-arm supporting arrangement including bearing meanswhich, when the arrangement is mounted on the phonograph, can beadjusted to determine the precise angular position of the tone-arm insaid bearings, and which is associated with shock absorbing means so asto prevent undesirable vibrational effects. An arrangement of this kindis especially advantageous when used for supporting tone-arm and pickupassemblies which are characterized by their light Weight and theirability to operate at exceedingly low needle-pressure, that is, aneedle-pressure of the order of'5 grams, because with assemblies of thischaracter, the support of the tone-arm in proper angular relationshiptothe playing surface. of the record is most critical, and theelimination of undesirable vibrations is most essential.

These and other objects, and the manner in which theyare obtained, willbe apparentfrom the following description based on the accompanyingdrawing which illustrates a preferred embodiment of the invention. Inthe drawing,

Figure 1 is an'end elevational view of a tonearm supporting arrangementconstructed inacr cordance with the invention;

Figure 2 is an elevational sectional view lookingin the generaldirection of arrows 2--2 in Figure 1; and

Figure 3 is a fragmentary view, on a reduced scale, looking in thegeneral direction of arrows 3--3 in Figure 1, and illustratingthe'adjustable feature of the bearing means for the tone-arm shaft.

Referring more particularly to the drawing,

the tone-arm I0 is provided with the usual shaft I l which constitutesthe pivot for swinging movement of the tone-arm aboutan'axisperpendicular to the playing surface of a record. For thatpurpose, the tone-arm shaft II is rotatably supported on a base 12 whichalso supports the customary turntable (not shown).

In accordance with the present invention, the means employed for thepurpose of rotatably supporting the tone-arm shaft H on base l2, in-

I cludes two spaced cooperatively disposed bearings l3 and IL. Onebearing l3 embracesthe shaft .at the upper portion thereof, that is, ata point adjacent its connection with the tone-arm. The other bearing I4engages the lower portion of said shaft and serves as a thrust bearing.

As more clearly shown in Figure 2, the upper bearing l3 has a generallycylindrical shape-andis advanta eously mounted, by means of 'arub bergrommet l5, on an upstanding protuberance l6 onthe base i 2. .Thegrommet tightly fits within and lines an aperture I1 in saidprotuberance, and snugly receives the bearing I3. In order to preventundue relative movement between bearing l3 and grommet I5, one endportion of said bearing is provided with a marginal rim I8 which abutsthe adjoining end of the grommet, and the other end of said bearing hasmeans, in the form of a split ring l9, which overlies the adjacent endof the grommet.

As also clearly shown in Figure 2, the lower bearing I4 is generallyT-shaped in cross-section, and is advantageously mounted by means of arubber grommet '20 on a bracket 2| which depends from the base l2. Thisgrommet 2U tightly fits within and lines an aperture 22 in said bracket,and snugly receives the shank of said bearing l4. Undue relativedisplacement between lower bearing I4 and associated grommet 20, isprevented by contact between. the head portion of said .bearing'and theadjoining end of the grommet, and by means of a split ring 23 arrangedon the shank portion of said bearing to overlap the adjacent end of saidgrommet. The head portion of lower bearing [4 is provided with asubstantially circular recess 24 having an inwardly tapered portion 25which terminates in a point to form a seat 26 for a correspondinglytapered tip portion 21 terminating the lower part of the tone-arm shaftI I.

The bracket 2|, in accordance with the invention, includes means wherebysaid bracket may be adjusted on the base l2. This adjustable featuremakes it possible to locate the lower bearing M in relation to the upperbearing l3, so that said bearings properly support the tonearm shaft IIin the correct angular position. For that purpose, the bracket, as shownin the drawing, is provided with a rigid elongated mounting plate 28which is adapted to be secured, by---means of screw-threaded elements 29and 30, to a pair of studs 34 and 32 extending from the under surface ofbase I2. These studs are provided with internally screw-threaded-bores33 and 34 which receive the securing elements 29 and 30, respectively.

As more clearly seen in Figure 2, the studs are disposed, generally, indiametrically opposed relationship on opposite sides of the protuberanceIS on which the upper bearing [3 is mounted, so'that said studs liesubstantially in a plane traversing the axial plane of said bearing. Theend portions'ofthe mounting plate 28 are provided with openings 35 and36 through which screw-threadedelements 29 and 39 pass to effect theconnection of the bracket to the base. The intermediate portion of themounting plate is also provided with an openingSI disposed toaccommodate the tone-arm shaft H supported in bearings l3 and M. It isto be particularly n'oted'that the opening 31, at the intermediateportion of the mounting plate is larger than the circumference of thetone-arm shaft, that the opening 35, at one end of said plate, is largerthan the circumference of the associated screwthreaded element 29, andthat the recess 24 of the lower bearing is larger than the tip portion21 of the tone-arm shaft. As illustrated in Figure 3, this constructionmakes it possible, prior to tightening of the screw-threaded elements,to

pivot-the mounting plate about the axis of one of said screw-threadedelements, that is the screw-threaded element 30, so that said plate 4which mounting plate 28 is a part, may be brought in the requiredposition with respect to the upper bearing I3, for the purposehereinbefore specified. It will be understood that, after the desiredadjustment is made, the adjusted relationship between the bearings issecured by tightening the fastening elements 29 and 30.

Accidental disengagement of the tone-arm shaft II from its bearings l3and I4 is effectively prevented by the provision of a stop associatedwith said shaft to limit its outward longitudinal movement. This stop isalso adjustable to take care of variations which may occur inmanufacturing and assembling of the parts. In practice, the stop isadvantageously provided by means of the so-called trip-arm, which isusually. connected to and movable with the tone-arm shaft. A portion ofthis trip-arm is shown at 38 and, in accordance with the invention, saidarm is rigidly attached, through its customary clamping portion 39, tothe tone-arm shaft 'at a point below the mounting plate 28. A spacer 49is conveniently interposed between said clamping portion of the trip-armand the mounting plate 28 so as to provide a uniform" abutting surfacefor contact with said plate, when outward movement of the tone-arm andits shaft occurs.

From the foregoing description, it will be ap-' preciated that theinvention provides a simple, yet effective, arrangement for supporting atonearm in proper operative position, and for absorbing vibrations whichmay result in undersirable frequency responses. Particularly, theadjustability of the arrangement is most advantageous in making itpossible to obtain the best operating results by the simple expedient ofadjustingthe relationship between the bearings I3 and M, without havingto disassemble the parts. The rubber grommets, which conveniently serveto mount the bearings, act to absorb shocks, thereby minimizing theeffects of undesirable vibra-' tions.

I claim:

1. In phonograph apparatus, a tone-arm, generally vertical shaftconnected to the tone-arm to support it over and in a plane generallyparallel to'the playing surface of a record, a supporting base having anupstanding protuberance and depending studs, an upper bearing arrangedon said protuberance and engaging the upper pore tion'of said shaft, abracket having an elongated mounting plate secured to said studs, asecond bearing arranged on said bracket and engaging the lower portionof said shaft, the end portions of the mounting plate being providedwith openings, and bolt-like fastening elements passing through saidopenings for engagement with the mentioned studs to effect theconnection of said plate to said studs, the opening at one end portionof said plate being larger than the circumference of its associatedfastening element to provide for lateral swinging displacement of thebracket and lower bearing, so as to adjust the angular position of saidshaft in the bearings thereby adjusting the angular position of thetone-arm in relation to the playing surface of the record.

2. The arrangement set forth in claim 1, in which the upper bearing isresiliently mounted on said protuberance, and the lower bearing isresiliently mounted on said bracket.

3. In phonograph apparatus, a tone-arm, a shaft connected with andextending at a substantially right angle from said tone-arm to sup-'port it over the playing surface of a record, a supporting base, a firstbearing mounted on said base and engaging said shaft at a point adjacentits connection with the tone-arm, a second bearing also mounted on saidbase and engaging said shaft at a point remote from its connection withthe tone-arm, the mounting of said second bearing including a brackethaving a portion provided with a pair of relatively spaced openings, andfastening elements passing through said openings and attaching saidmember to the supporting base, one of said openings being larger thanthe cross-sectional dimension of the associated fastening element toprovide for swinging displacement of said member and second bearing 1 ina plane transverse to said shaft to adjust the angular position of thelatter in the bearings thereby adjusting the angular position of thetone-arm in relation to said surface of the record.

4. In a phonograph apparatus, a tone-arm, a

- generally vertical shaft connected to the tonearm to support it overand in a plane generally parallel to the playing surface of a record, anupper bearing engaging an upper portion of said shaft, a second bearingengaging a lower portion of said shaft, a supporting base carrying oneof said bearings, a bracket secured to said'base and carrying the otherof said bearings, said bracket having a pair of relatively spacedopenings, and fastening elements passing through said openings forengagement with said base, one of said 5 openings being larger than thecross-sectional dimension of the associated fastening element to providefor lateral swinging displacement of the bracket and the bearing carriedthereby, so as to adjust the angular position of said shaft in thebearings thereby adjusting the angular position of the tone-arm inrelation to the playing surface of a record.

5. The arrangement set forth in claim 4, in which one bearing isresiliently mounted on said base, and the other bearing is resilientlymounted on said bracket.

LOUIS C. AMMLUNG, J R.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

